Heat a large skillet. Add olive oil and garlic and let the garlic cook, stirring, until aromatic and lightly colored.
Add the onions to the skillet along with salt and ground black pepper to taste. Saute for a few minutes until the onions have softened.
Add the kale to the pot and cook until it has wilted. Add the butternut squash cubes along with the cashews, herbs and red pepper flakes. Mix well.
Continue cooking for a few minutes, stirring frequently, until the butternut squash cubes are slightly tender but not fully cooked. They will continue cooking in the oven. Set the filling aside to cool.
Set a rack in the lowest position in the oven. Preheat the oven to 400 degrees Fahrenheit.
Roll out one pie or puff pastry crust and line a 2 ½ or 3 quart baking dish with it. Tuck any overhanging dough underneath at the edges.
Pour in the kale and butternut squash filling and spread it around evenly. Top with the vegan cheese shreds. Place the baking dish in the fridge while you roll out the top crust.
Place the top crust over the kale-butternut filling and fold in any overhanging dough. Crimp the edges with a fork and cut vents in the top crust to help any steam escape. Place the baking dish on a baking sheet.
Bake the pie in the preheated oven for 50 minutes to an hour. The butternut squash should feel tender and a knife should go cleanly through, or give more time.
Let the pie stand for 15 minutes before serving.